The aim of this project is to demonstrate an immunometric assay for Hepatitis B Surface Antigen (HBsAg) using Acridinium esters as a chemiluminescent label. This will lead to a technique for the detection of viral antigens that requires exquisite sensitivity, by a method which is simpler, safer, and cheaper than conventional methods. Monoclonal antibodies to HBsAg will be covalently labeled with an acridinium ester to a high specific luminescence activity. These will then be used in commercial kits to develop a sensitive chemiluminescence assay. Other acridinium esters will also be tested in these assays. After assay optimization the chemiluminescence assay will be compared with immunoradiometric assays and detection limits using HBsAg panels determined. The research is expected to provide an HBsAg assay with lower detection limits, using stable reagents. The assay should be safer, simpler and cheaper than commercial assays, with a greater slope aiding the precision of detection. This work would lead to Phase II production of antibodies, improved chemiluminescent compounds, assay configurations, prototype instrument design and development, and clinical trials. The multimillion dollar viral antigen immunoassay market would readily accept a chemiluminescence assay with the advantages the technology has to offer.